Conventional electronic components such as transistors, switches, logic components and the like, are relatively heavy and rigid, and typically mounted to a rigid fibreglass printed circuit board (PCB). However, there is a growing need for “soft” or flexible electronics.
Dielectric elastomer devices (DED), for example, are transducers which utilize high voltage, low current electric charge to convert between mechanical and electrical energy, comprising a deformable dielectric membrane between opposing compliant electrodes. The devices have in the past been be used as actuators (referred to as a dielectric elastomer actuator or DEA) or generators (referred to as a dielectric elastomer generator or DEG).
One of the advantages of DEDs is that they are lightweight and flexible, making them particularly suited to applications where traditional actuators and/or generators are not possible or practical. However, control of DEDs generally requires conventional and relatively heavy and rigid electronic components which negate some of the advantages of the DED.
International Patent Publication No. WO 2011/105913 discloses an electric circuit device comprising a conductive element coupled to a deformable body, the conductive element having variable resistivity based at least in part on deformation of the deformable body. The variable resistivity or piezoresistivity of the conductive element is achieved using a composite of conductive particles in a non-conductive matrix. As the DED membrane stretches, the density of conducting particles also changes, and due to percolation the resistivity may change by orders of magnitude. In particular, substantial changes in resistance occur at the percolation threshold.
The electric circuit device of WO 2011/105913 may therefore be used as a dielectric elastomer switch (DES), enabling analogue and/or digital or Boolean circuitry to be integrated into the dielectric elastomer device. Doing so provides “soft” electronics for controlling an actuator or generator without any external circuitry, eliminating off-membrane circuitry and permitting simple fabrication (the DED and conducting element or sensor being made of the same materials, in the same process).
A DES is useful for switching high voltage signals and can be printed onto dielectric elastomer surfaces using the same technology for making the DEDs themselves.
However, the soft switches of the prior art (including WO 2011/105913) generally suffer from one or more disadvantages which may include unpredictable or inconsistent behaviour, linearity in the resistance/deformation relationship, unsuitability for integration with DEDs, the need for hand fabrication, and/or difficulties in automating fabrication.